Pre-glacial to full glacial sedimentation along the Pacific margin of West Antarctica: Record of shifting pattern of supply and transport


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Karsten.Gohl [ at ] awi.de

Abstract

The seismic sediment record of the Amundsen Sea continental rise provides insight into the sedimentation processes from pre-glacial to glacial times, variations in ocean-bottom circulation, early ice sheet growth, and intensification towards the present icehouse regime. Seismic reflection data acquired during the 2010 RV Polarstern and the 2006 RV Tangaroa expeditions, created a 2000 km long continuous Amundsen Sea to Ross Sea seismic transect. Pre-existing lines linked to this transect, connect key seismic stratigraphy horizons from the Ross Sea shelf to the rise and farther along the West Antarctic margin, up to the Amundsen Sea Embayment. Seismic units AS-1 to AS-3 constitute the Cretaceous to Eocene pre-glacial (PG) sequence, units AS-4 to AS-6 the Eocene to mid-Miocene transitional (T) sequence, and units AS-7 to AS-11 the mid-Miocene to Quaternary full glacial (FG) sequence. The top PG sequence boundary horizon AS-u3/uPG-T links to unconformity RSU6 of the Ross Sea shelf and to the base of Unit II of the eastern Amundsen Sea, and is interpreted as the first arrival of grounded ice on the shelf. The top T sequence boundary AS-u6/uT-FG, links to RSU4 and the base of Unit III, and is interpreted as the onset of the FG regime with intensified ice sheet advances onto the outer shelves. The constructed pre-glacial sediment thickness grid depicts 1.3-4.0 km thick depocenters on the continental rise, relatively evenly distributed along the margin. The depocenters change markedly in the transitional phase at or after the Eocene/Oligocene boundary when first major ice sheets reached the shelf. Full glacial sequences, starting in the middle Miocene, indicate new depocenter formation in front of the Amundsen Sea Embayment and a localized eastward shift in the Bellingshausen Sea and Antarctic Peninsula basins. Using present-day drainage paths and source areas on the continent, we calculated volumes of eroded sediment for the pre-glacial, transitional and full glacial stages. In total, an estimated volume of about 10.2 x 106 km3 was eroded from West Antarctica and transported into the Pacific since separation of New Zealand in the Late Cretaceous.



Item Type
Conference (Poster)
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Primary Division
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Peer revision
Not peer-reviewed
Publication Status
Published
Event Details
SCAR Open Science Conference, 10 Aug 2016 - 20 Aug 2016, Kuala Lumpur, Malaysia.
Eprint ID
40460
Cite as
Lindeque, A. , Gohl, K. , Wobbe, F. , Uenzelmann-Neben, G. , Henrys, S. and Davy, B. (2016): Pre-glacial to full glacial sedimentation along the Pacific margin of West Antarctica: Record of shifting pattern of supply and transport , SCAR Open Science Conference, Kuala Lumpur, Malaysia, 10 August 2016 - 20 August 2016 .


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